Multipart/form-data请求为空

Question

我正在尝试上传一张图片和一些MultipartFormDataContent对象中的json数据。但是由于某些原因，我的webapi没有正确地接收请求。最初，api使用415响应直接拒绝该请求。为了解决这个问题，我向WebApiConfig.cs添加了一个用于多部分/表单数据的xml格式化程序

 public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services
        // Configure Web API to use only bearer token authentication.
        config.SuppressDefaultHostAuthentication();
        config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));
        config.Formatters.XmlFormatter.SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("multipart/form-data"));

        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{action}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }

这似乎在很大程度上是有效的，我使用ARC测试了它，它接收到了multipart的所有部分，唯一的问题是字符串内容没有出现在表单中，它出现在文件中，但我将其归因于请求没有格式化为StringContent对象。

我目前遇到的问题是，我的Xamarin应用程序在发送多部分请求时似乎没有发布任何内容。当请求到达API控制器时，内容标头和所有内容都在那里，但是文件和表单字段都是空的。

在做了一些研究之后，我似乎不得不写一个自定义的MediaTypeFormatter，但我找到的似乎没有一个是我正在寻找的。

下面是我的代码的其余部分：

Api控制器：

[HttpPost]
    public SimpleResponse UploadImage(Image action)
    {
        SimpleResponse ReturnValue = new SimpleResponse();

        try
        {
            if (HttpContext.Current.Request.Files.AllKeys.Any())
            {
                var httpPostedFile = HttpContext.Current.Request.Files["uploadedImage"];
                var httpPostedFileData = HttpContext.Current.Request.Form["imageDetails"];

                if (httpPostedFile != null) 
                {
                    MiscFunctions misctools = new MiscFunctions();

                    string fileName = User.Identity.Name + "_" + misctools.ConvertDateTimeToUnix(DateTime.Now) + ".jpg";
                    string path = User.Identity.Name + "/" + DateTime.Now.ToString("yyyy-mm-dd");
                    string fullPath = path + fileName;

                    UploadedFiles uploadedImageDetails = JsonConvert.DeserializeObject<UploadedFiles>(httpPostedFileData);

                    Uploaded_Files imageDetails = new Uploaded_Files();

                    imageDetails.FileName = fileName;
                    imageDetails.ContentType = "image/jpeg";
                    imageDetails.DateCreated = DateTime.Now;
                    imageDetails.UserID = User.Identity.GetUserId();
                    imageDetails.FullPath = fullPath;

                    Stream imageStream = httpPostedFile.InputStream;
                    int imageLength = httpPostedFile.ContentLength;

                    byte[] image = new byte[imageLength];

                    imageStream.Read(image, 0, imageLength);

                    Image_Data imageObject = new Image_Data();
                    imageObject.Image_Data1 = image;

                    using (var context = new trackerEntities())
                    {
                        context.Image_Data.Add(imageObject);
                        context.SaveChanges();

                        imageDetails.MediaID = imageObject.ImageID;
                        context.Uploaded_Files.Add(imageDetails);
                        context.SaveChanges();
                    }

                    ReturnValue.Success = true;
                    ReturnValue.Message = "success";
                    ReturnValue.ID = imageDetails.ID;
                }
            }
            else
            {
                ReturnValue.Success = false;
                ReturnValue.Message = "Empty Request";
                ReturnValue.ID = 0;
            }
        }
        catch(Exception ex)
        {
            ReturnValue.Success = false;
            ReturnValue.Message = ex.Message;
            ReturnValue.ID = 0;
        }

        return ReturnValue;
    }

Xamarin应用程序Web请求：

public async Task<SimpleResponse> UploadImage(ImageUpload action)
    {
        SimpleResponse ReturnValue = new SimpleResponse();

        NSUserDefaults GlobalVar = NSUserDefaults.StandardUserDefaults;
        string token = GlobalVar.StringForKey("token");

        TaskCompletionSource<SimpleResponse> tcs = new TaskCompletionSource<SimpleResponse>();

        try
        {
            using (HttpClient httpClient = new HttpClient())
            {
                httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
                httpClient.DefaultRequestHeaders.Add("Accept", "application/xml");

                using (var httpContent = new MultipartFormDataContent())
                {
                    ByteArrayContent baContent = new ByteArrayContent(action.Image.Data);
                    baContent.Headers.ContentType = new MediaTypeHeaderValue("Image/Jpeg");

                    string jsonString = JsonConvert.SerializeObject(action.UploadFiles);

                    StringContent stringContent = new StringContent(jsonString);
                    stringContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

                    using (HttpResponseMessage httpResponse = await httpClient.PostAsync(new Uri("http://10.0.0.89/api/Location/UploadImage"), httpContent))
                    {
                        string returnData = httpResponse.Content.ReadAsStringAsync().Result;

                        SimpleResponse jsondoc = JsonConvert.DeserializeObject<SimpleResponse>(returnData);

                        ReturnValue.ID = jsondoc.ID;
                        ReturnValue.Message = jsondoc.Message;
                        ReturnValue.Success = jsondoc.Success;
                    }
                }
            }
        }
        catch(WebException ex)
        {
            ReturnValue.Success = false;

            if (ex.Status == WebExceptionStatus.Timeout)
            {
                ReturnValue.Message = "Request timed out.";
            }
            else
            {
                ReturnValue.Message = "Error";
            }

            tcs.SetResult(ReturnValue);
        }
        catch (Exception e)
        {
            ReturnValue.Success = false;
            ReturnValue.Message = "Something went wrong";
            tcs.SetResult(ReturnValue);
        }

        return ReturnValue;
    }

Answer 1

在尝试发送内容之前，您没有将部件添加到内容中

//...code removed for brevity

httpContent.Add(baContent, "uploadedImage");
httpContent.Add(stringContent, "imageDetails");

//...send content

在服务器端，您可以检查以下答案

Http MultipartFormDataContent

关于如何读取传入的多部分请求

Answer 2

try
   {
var jsonData = "{your json"}";
var content = new MultipartFormDataContent();

content.Add(new StringContent(jsonData.ToString()), "jsonData");
try
   {
     //Checking picture exists for upload or not using a bool variable
     if (isPicture)
       {
         content.Add(new StreamContent(_mediaFile.GetStream()), "\"file\"", $"\"{_mediaFile.Path}\"");
       }
     else
      {
         //If no picture for upload
         content.Add(new StreamContent(null), "file");
      }
   }
  catch (Exception exc)
   {
      System.Diagnostics.Debug.WriteLine("Exception:>" + exc);
   }

var httpClient = new HttpClient();
var response = await httpClient.PostAsync(new Uri("Your rest uri"), content);

 if (response.IsSuccessStatusCode)
 {
   //Do your stuff  
 } 
}
catch(Exception e)
 {
 System.Diagnostics.Debug.WriteLine("Exception:>" + e);
}

其中_mediaFile是从图库或相机中选择的文件。https://forums.xamarin.com/discussion/105805/photo-json-in-xamarin-post-webservice#latest